Local physicians will be asked to refer approximmtely 36 hyperactive children in grades 3-5 who are receiving stimulant medication. After obtaining parental consent, a 3-week assessment will be made including physiological measures, neurological assessment, teacher ratings, academic achievement data, classroom observation, parent ratings, and observations of parent-child interactions. During this assessment phase, the children will be evaluated both on and off medication. Children will be accepted for the project if they meet the criteria of being both hyperactive and responders to the medication. Following random assignment to either a drug therapy or behavior therapy group, a 16-week treatment phase will be instituted. Periodic assessments will be made during treatment. The drug therapy will consist of the medication regimen recommended by the family physicians except that all of these children will receive a single morning dosage. The children in the behavior therapy group will be taken off medication. Parents and teachers will be trained to use various behavioral procedures (such as systematic attention, daily report cards and other incentive programs) to shape and maintain the children's academic and social behaviors both at home and in school. Therapist contact and some of the treatment procedures will be gradually withdrawn. During the 3-week post-treatment assessment phase, the drug therapy children will be evaluated without medication. The behavior therapy children will be evaluated with only natural teaching and parenting skills being used during this period. In addition to comparing the effectiveness of drug and behavior therapy, we hope to evaluate the extent to which our assessment measures can predict the response of the children to treatment.